Public servants have been warned that the greatest challenge for the Croke Park agreement lies ahead.

Brendan Howlin, Minister for Public Expenditure and Reform, said while the burden of cuts is already being felt, more have to be made as the deal on pay and reform is imposed.

He told delegates at the Institute of Public Administration (IPA) conference that resources will be squeezed further and staff numbers will fall while responsibilities to citizens remain the same.

"I know that the burden of reductions in expenditure and staff numbers is being acutely felt by staff across the public service," he said. "I wish that further cuts were avoidable. But the harsh reality is that they are not."

Mr Howlin said the public service reform programme is the most ambitious and far-reaching since the founding of the State.

He added: "Our challenge is to maintain critical frontline services to the greatest extent possible with the substantially reduced resources available, and I believe that the Croke Park agreement is a critical lever for enabling change in this context.

"It is clear that reform on this scale and level of complexity cannot simply be imposed on an unwilling workforce of 300,000 people.

"The reality is that we need the buy-in of staff at all levels across the public service if this is to work.

"The real value of the Croke Park agreement is that it has secured staff co-operation with the 'tools of change' - redeployment, reform and reconfiguration of services - which will be critical as staff numbers and resources continue to be significantly reduced."

Meanwhile, Richard Boyle, IPA head of research, told the conference each minister in charge of a department should in effect become his or her own finance minister to reduce waste of public money and produce better outcomes in public service.